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A common way of permanently joining optical telecommunications fibers is with a fusion splice, thereby forming a continuous glass strand. The splice is formed by carefully removing the protective polymer buffer that surrounds the fibers near the ends to be spliced. The bare fiber ends are cleaved and cleaned. The end faces of the fibers are placed in contact, and the fibers are fused together with heat from a torch or electric arc. This type of splice provides robust low loss transmission between the spliced segments. In the splice region, the fiber may be recoated to protect the bare glass or it may be packaged in a surrounding protective housing.
This type of splice has, however, several disadvantages. The protective splice housing is typically long. Some splice packages are as long as 2.375 inches in length. In addition, the fiber emerges from both ends of the splice package. Because the recommended bend radius of the fiber is approximately one inch, it may be necessary to leave as much as an additional inch at each end of the splice package to allow the fibers to bend into another direction.
This combination of long splice package, large bend radius of the fiber, and emergence of the fiber from both ends of the housing may cause difficulty in packaging splices compactly. For example, if it is desired to splice together the pigtails from two fiber optic splitters, each of which may reside in a package more than two inches in length, the splice may add an additional three or four inches to the overall length to allow for bends and pigtails from the components. The end to end length of two spliced splitters can easily be ten inches or more. See FIG. 5. To accommodate this inconveniently long length, the fibers are often coiled in a box, as shown in FIG. 6. This configuration results in a lesser overall length, but a greater overall area.
As noted above, a turn or bend in an optical fiber typically requires a bend radius of 2 cm or more to avoid light loss and maintain a useful longevity in an unprocessed bent fiber. It is also known that this radius may be substantially reduced to as little as 50xcexc using a miniature bend. To form a miniature bend, the diameter along a length of bare fiber is reduced to as little as 1xcexc, by, for example, drawing, etching, or a combination thereof. In the reduced diameter region, the fiber conducts light by internal reflection at least partially due to the difference in index of refraction at the interface between the fiber and the surrounding environment, generally air. Thus, in this region, the fiber may be bent with no substantial light loss from the bend. See U.S. Pat. Nos. 5,138,676 and 5,452,393, the disclosures of which are incorporated by reference herein.
The present invention provides a fiber optic device having a miniature bend splice for changing direction along a fiber optic path in a compact space.
More particularly, the device comprises a first optical fiber having a first end portion and a second optical fiber having a second end portion. The first end portion and the second end portion are joined at a fusion splice in a fusion splice region. A miniature bend is formed in at least a portion of the fusion splice region that has a diameter reduced to less than a diameter of the first optical fiber and the second optical fiber and is capable of transmitting light with substantially less light loss due to bending than an unreduced fiber portion. The splice and bend are preferably housed in a suitable support structure or packaging. In this manner, the bend provides a change of direction between the first optical fiber and the second optical fiber in a compact space.
The fusion splice and miniature bend fiber optic device is particularly useful in the routing of optical fibers in the field. Often, the technician laying new optical fiber or repairing existing fibers must determine or accommodate an appropriate and efficient routing in the field and must bend the fibers as necessary to achieve this routing. The present invention allows the technician to splice two fibers and then bend the splice region to a desired angle in the field so that the fiber heads in the desired direction. The device is also particularly useful in combination with two fiber optic splitters that must be spliced together. The combination of two splitters and a miniature bend splice may be housed in a highly compact package.